Chemistry OCR Gateway - C2 Notes

Chemistry C2 Topic Notes 

 

 

Periodic Table 

 

Dmitri Mendeleev. It is in the order of atomic mass and it keeps elements with similar properties in the same vertical. 

The group which they belong to, corresponds to the number of electrons

Rows are called periods and each new period represents another full shell of electrons 

 

Electron shells 

 

Electronic configuration order: 2,8,8 – these electrons occupy the shells

 

Ionic Bonding 

 

Ions are charged particles 

Full outer shell = stable electronic structure 

When metals form ions, they lose electrons to form positive ions

When non-metals form ions, the gain electrons to form negative ions 

 

Group 1+2 = Metals – lose electrons to form positive ions (cations)

Group 6+7 = Non-metals. Gain electrons to form negative ions (anions)

 

Group 1+2 = easier to remove from outer electrons form ions and are more reactive 

Group 6+7 = harder for nucleus to attract extra electrons and it gets less reactive 

 

Ions with opposite charges form ionic bonds 

 

When a metal and a non-metal react together the metal can lose electrons to form a positively charged ion 

 

Oppositely charged ions are then strongly attracted to another by electrostatic forces and form an ionic bond 

 

Ionic compounds

 

Dot and cross diagrams are used to show ionic compounds 

Dots = electrons 

Crosses = Other Electrons 

 

Ionic compounds have giant lattice structures, strong electrostatic forces of attraction between oppositely charged ions 

 

Ionic compounds all have similar properties 

-        High melting and boiling point because of strong attraction 

-        Solid ionic compounds don’t conduct electricity because ions are fixed in place and cant move. 

-        Ions are free to move and will carry on electric current 

-        Easily dissolve in water  

 

Simple Molecules 

 

Covalent Bonding (Sharing Electrons)

 

Non-metals combine – form covalent bonds by sharing pairs of electrons 

Both atoms have full outer shells 

Each covalent bond provides an extra shared electron 

 

Simple molecular substances have low melting and boiling point 

-        Atoms within the molecules held by very strong covalent bonds 

 

By contrast, forces of attraction between these molecules are very weak. They don’t conduct electricity because no free electrons are ions 

 

Giant Covalent structures or fullerenes

 

Similar to ionic lattices except there are no charged ions

Atoms are bonded to each other by strong covalent bonds 

Don’t conduct…